The purpose of the proposed research is to gather evidence supporting the hypothesis that genetic duplication is a fundamental event underlying (a) the evolution of enzymes that mediate sequential, catalytically different, metabolic reactions and (b) intragenic mutations leading to the evolutionary divergence of proteins. Preliminary studies indicate that the two processes operated in the evolution of the beta-ketoadipate pathway: (a) Enzymes mediating two sequential metabolic reactions possess homologous amino terminal amino acid sequences, and (b) Comparison of the amino acid sequences repeated within one protein, muconolactone isomerase, suggest that recombination between misaligned chromosomes produced patterns of repetition and deletion in its primary structure. Amino acid sequences gathered in the proposed research will test the predictive value of the misaligned recombination hypothesis. The investigation may provide the first conclusive sequence evidence supporting the view that enzymes catalyzing biochemically distinct, metabolically sequential reactions share a common evolutionary origin. Finally, the information gathered in this study may set stage for investigations in which the proposed recombinational events take place in the laboratory.